WO2017108556A1

WO2017108556A1 - Method for operating an electric motor coolant compressor

Info

Publication number: WO2017108556A1
Application number: PCT/EP2016/081111
Authority: WO
Inventors: Hans-Joachim Schröder
Original assignee: Brose Fahrzeugteile GmbH & Co. Kommanditgesellschaft, Würzburg
Priority date: 2015-12-23
Filing date: 2016-12-15
Publication date: 2017-06-29
Also published as: US20190047372A1; US10737554B2; KR102185147B1; DE102016207129A1; KR20180097689A; CN108603794A; CN108603794B

Abstract

The invention relates to a method (76) for operating an electric motor coolant compressor (12) of a motor vehicle (2). A first temperature (80) of a power semiconductor (66) is measured, and a second temperature (84) of the power semiconductor (66) is determined using a theoretical model (86) of the electric motor coolant compressor (12). The difference (96) between the first temperature (80) and the second temperature (84) is determined. An error (104) is detected if the difference (96) is greater than a first threshold (100). The invention further relates to an electric motor coolant compressor (12) of a motor vehicle (2), to the use of an electric motor coolant compressor (12), and to a motor vehicle (2) comprising a coolant circuit (8).

Description

description

Method for operating an electromotive refrigerant compressor

The invention relates to a method for operating an electromotive refrigerant compressor of a motor vehicle and to an electromotive refrigerant compressor of a motor vehicle, which comprises a power semiconductor. Power semiconductors here are understood to be a semiconductor, in particular a semiconductor switch, which can carry an electrical current of at least 1 A. The invention further relates to the use of an electromotive refrigerant compressor and a motor vehicle having a refrigerant circuit comprising an electromotive refrigerant compressor.

Motor vehicles usually have an air conditioner, by means of which a temperature control of an interior of the motor vehicle takes place. Also, when powered by an electric motor vehicles, the required energy storage, such as a high-voltage battery, cooled. The air conditioning system has a refrigerant circuit, which comprises a refrigerant compressor, downstream of a condenser and this fluidly downstream of an evaporator. This is fluidly connected downstream of another heat exchanger, which is in thermal contact with a fan line leading into the interior of the motor vehicle, or with any energy cells of the high-voltage energy storage. The refrigeration cycle is filled with a refrigerant, such as R134a, R1234yf or C02.

During operation, a pressure of the refrigerant is increased by means of the refrigerant compressor, which leads to an increase in the temperature of the refrigerant. This is conducted to the condenser, which is in thermal contact with an environment of the motor vehicle. In this case, a temperature reduction of the refrigerant, which is in turn relaxed in the downstream evaporator to the original pressure, which is why the temperature of the refrigerant is further reduced. In the downstream heat exchanger is transferred from the thermally contacted with the heat exchanger component thermal energy to the refrigerant, resulting in a cooling of the component and heating of the refrigerant. The heated refrigerant is again supplied to the refrigerant compressor for closing the refrigerant cycle.

The refrigerant compressor is usually driven by a belt drive from an internal combustion engine of the motor vehicle and has a compressor head, which is for example a scroll compressor head. If the air conditioning system is a component of a motor vehicle that does not include an internal combustion engine, the refrigerant compressor has an electric motor, by means of which the compressor head is driven. Here, the rotational speed of the drive and thus the cooling capacity of the air conditioner is adjusted based on a temperature setting of a user of the motor vehicle or a realized temperature of the high-voltage battery.

The invention has for its object to provide a particularly suitable method for operating an electromotive refrigerant compressor of a motor vehicle and an electromotive refrigerant compressor of a motor vehicle and a particularly suitable motor vehicle with an electromotive refrigerant compressor, in particular increases security and preferably manufacturing costs are reduced.

With regard to the method, this object is achieved by the features of claim 1, in terms of the electromotive refrigerant compressor by the features of claim 7 and in terms of the motor vehicle by the features of claim 10 according to the invention. Advantageous developments and refinements are the subject of the respective subclaims.

The method is used to operate an electromotive refrigerant compressor, which consequently comprises an electric motor drive with an electric motor. Of the Electromotive refrigerant compressor is in particular a component of a refrigerant circuit of the motor vehicle, by means of which, for example, a temperature of the interior of the motor vehicle and / or a cooling of an energy storage of the motor vehicle. In particular, the electromotive refrigerant compressor comprises a compressor head, for example a scroll compressor. Particularly preferably, a refrigerant is compressed by means of the electromotive refrigerant compressor, in particular a chemical refrigerant such as R134a or R1234yf. Alternatively, C02 is used as the refrigerant. The electric motor is particularly preferably a brushless electric motor, preferably a brushless DC motor (BLDC).

The electromotive refrigerant compressor comprises a power semiconductor, in particular a power semiconductor switch. The power semiconductor is in this case provided and configured to carry an electrical current of at least 1A, 2A, 5A or 10A, preferably to switch. In particular, current is supplied to the electric motor by means of the power semiconductor, for which, in particular, pulse width modulation takes place by means of the power semiconductor switch. In other words, a PWM signal is output by means of the power semiconductor switch, which is preferably fed into a coil winding of the electric motor, in particular a stator of the electric motor. Advantageously, the power semiconductor is subjected to a PWM control of a driver circuit, in dependence of which the power semiconductor switch is set from an electrically conductive to an electrically non-conductive state. The electromotive refrigerant compressor in particular comprises an electronic converter, which is fed, for example, from a DC voltage network. The converter preferably has a power output stage, which comprises the power semiconductor switch, in particular a number thereof. The power semiconductor switches can switch the required electric power for the required performance of the electric motor used. In other words, the power semiconductor switches are provided and configured to be capable of switching an electric current that corresponds to the current required for the phase windings of the electric motor being used. In particular, when operating on the power semiconductor switch, if this is in the electrically non-conductive state, an electrical voltage, which is intended for the intended voltage range of the supply of the compressor. These can be voltages from a few volts to about 1000V. For example, the electrical voltage is 12V, 24V or 48V. In particular, the electric refrigerant compressor is electrically contacted with an electrical system of the motor vehicle, which leads, for example, an electrical voltage of 12V, 24V or 48V. Alternatively, the voltage applied to the power semiconductor switch or having the electrical system is 288V, 450V, 650V or 830V.

The method provides that in a first step, a first temperature of the power semiconductor is measured, for which a temperature sensor is used in particular. In other words, we determine the temperature of the power semiconductor directly, for which purpose, for example, a thermometer, a thermoresistor or the like is used. Alternatively, the heat radiation of the power semiconductor is detected.

In a second step, which can be carried out, for example, simultaneously with the first step, but also before or after this, a second temperature of the power semiconductor is determined. In particular, a time offset between the first and the second operation is less than or equal to 30 seconds, 20 seconds, 10 seconds or 1 second. The second temperature is determined on the basis of a theoretical model of the electromotive refrigerant compressor, in particular of the electric motor, for which, for example, an electrical voltage applied to the power semiconductor, an operating time of the power semiconductor and / or an electric current carried by the power semiconductor is used for the determination. Alternatively or preferably in combination with this, a thermal model of the electromechanical structure and / or an information about an expected speed available via the control of the electromotive refrigerant compressor is used for the determination. The information enables a model-based, in particular in connection with a detected, in particular measured, characteristic of the electric current and / or the electrical voltage Statement about the expected performance and the anticipated second temperature. In particular, the number of switching operations performed by means of the power semiconductor switch is used. Suitably, a power loss of the power semiconductor is used to determine the second temperature. Advantageously, the control signals, which are created by means of the PWM -An control used to determine the second temperature, if this is present. For example, the second temperature is determined using a map or a formula.

In a subsequent further working step, a difference between the first temperature and the second temperature is determined. In other words, the deviation of the second temperature is determined to the first temperature, for which the second temperature is subtracted from the first temperature. In particular, in this case, the difference is determined with a sign, so that the difference is greater than zero (0), if the second temperature is less than the first temperature. In this way, a temperature entry in the power semiconductor is determined, which would not be explained by the operation of the electric motor by means of the theoretical model. Such a temperature increase is thus caused due to a malfunction of other components of the electric motor, such as a mechanical malfunction of a compressor head of the refrigerant compressor. In an alternative to this, the difference is determined without sign, that is to say the amount of the deviation between the two temperatures is determined, and thus in particular a target corridor of an expected value for the first temperature is determined. In this way, any malfunction within the refrigerant circuit can also be detected. In another step, an error is detected if the difference is greater than a first limit.

Due to the method is thus made possible to identify a fault of the mechanical components before a total failure of the electromotive refrigerant compressor takes place. It also makes it possible to avoid overloading, which increases safety. In particular, the method of operation is also used for other ancillary components of the motor vehicle, for example an electromotive seat adjustment or a radiator fan, for which the theoretical model is adjusted accordingly. In other words, the invention is independent of the specific use within a refrigerant compressor.

In particular, the first limit value is determined on the basis of the current calculated model. For example, the first limit is 0 ° C. In other words, an error is detected if the second temperature does not exactly correspond to the first temperature. Conveniently, the first limit is always positive. In other words, a cooling of the power semiconductor, for example due to an energy transfer to a conveyed by means of the electromotive refrigerant compressor refrigerant due to an otherwise dissipation of thermal energy is not considered. Most preferably, the first limit is greater than or equal to 2 ° C, 5 ° C or 10 ° C. Thus, by means of the first limit value, short-term temperature fluctuations and / or a reduced / delayed heat conduction of components of the electromotive refrigerant compressor are taken into account. In particular, the first limit is less than or equal to 20 ° C, which is why excessive heating of the electric motor due to a malfunction is excluded, which could otherwise lead to thermal failure, for example, the power semiconductor or the temperature sensor. Preferably, the second temperature is determined at a different time than the first temperature. In this way, a reduced / delayed heat conduction of components of the electromotive refrigerant compressor is taken into account. In summary, the comparison is delayed in time. For example, the comparison is carried out not only by adding a suitable tolerance compensation, in particular by adjusting the first limit, but is also evaluated delayed in time.

Advantageously, a power of the electric motor is reduced when the first temperature is greater than a second threshold. For this purpose, a speed and / or torque of the electric motor is expediently reduced, in particular the maximum power of the electric motor is reduced to a reduced power and consequently limited. Conveniently, the second limit is less than or equal to the specification-related temperature limit for the used Power semiconductors. For example, the second limit is less than or equal to 140 ° C, 130 ° C, 120 C or 100 ° C. In this way, thermal damage of the power semiconductor or other components of the electromotive refrigerant compressor due to an elevated temperature is substantially excluded. Since the directly measured first temperature is used for this, a susceptibility to errors is reduced. In particular, the power is reduced by a suitable amount, in particular to at least half. Alternatively, the power is reduced to zero (0) and thus the electric motor is stopped, at least until the first temperature is below the second threshold, preferably below the second threshold minus a suitable safety margin, such as 10 ° C, 20 ° C or 5 ° C is.

Suitably, based on the first temperature and the second temperature, a temperature of the conveyed by means of the electric motor refrigerant is determined. In particular, the difference between the first temperature and the second temperature is used for this purpose. Due to the refrigerant, there is a supply or discharge of thermal energy to the power semiconductor, in particular via a housing of the refrigerant compressor. Thus, due to the comparison between the first and the second temperature, the thermal energy supplied or discharged by means of the refrigerant can be determined. Based on the volume of refrigerant conveyed by means of the electromotive refrigerant compressor, it is thus possible to determine the temperature of the refrigerant at least in a specific region of the electromotive refrigerant compressor. For this purpose, no additional temperature sensor must be provided, which must be introduced into the volume flow of the refrigerant and must be chemically resistant to the pumped refrigerant. As a result, manufacturing costs are reduced. The determination of the temperature of the refrigerant based on the first temperature and the second temperature, and in particular on the basis of a thermal model of the electromotive refrigerant compressor, preferably the electric motor, is independent of the detection of the error and is considered rather as an independent invention. Preferably, an error is detected if the temperature of the pumped refrigerant is greater than a third threshold. Here, the third limit value is matched to the electromotive refrigerant compressor and its application. If, therefore, by means of the refrigerant compressor or other components of the refrigerant circuit is no longer sufficient cooling, the error is detected. Consequently, an error is detected even before a thermal failure due to a lack of cooling, which further increases security.

Preferably, the gradient of the difference is determined. In particular, the first temperature is measured several times at time intervals, which are preferably the same, and compared with a respective associated second temperature, which is determined based on the theoretical model, for example, calculated to form a difference in each case. If the change in the difference within a defined number of time intervals within which the difference was respectively determined, ie within which, for example, the measurement and model-based determination of the two temperatures has been made, exceeds a fourth limit value, e.g. is suitably selected, and in particular a speed value in temperature per time, for example, the error is also detected, and preferably there is a power reduction or a shutdown of the electric motor. In this way, both a static and a dynamic overload detection is given, which ensures the operation of the electromotive refrigerant compressor, even in extreme situations. Alternatively or in combination, a minimum operation can be maintained even in the event of a fault. In summary, in addition to the criterion of the (absolute) difference between the first temperature and the second temperature (difference between the measured and the calculated temperature), which is used in particular for power reduction or to shut down the unit, and the gradient of the difference for determination considered the error.

Preferably, the power of the electric motor is reduced if an error is detected. For example, the power is set at 75%, 50% or 25% of the nominal reduced. In particular, the electric motor is stopped if an error is detected. In this way, damage to other components of the motor vehicle, in particular the electromotive refrigerant compressor, excluded. Alternatively or in combination, a warning is issued when the error is detected. In particular, this is output on a display of the motor vehicle, so that a driver of the motor vehicle is informed about the error. In this way, it is possible for the driver to shut down the motor vehicle before further damage to components of the motor vehicle takes place. The driver can also respond to a failure of a cooling capacity of the electromotive refrigerant compressor and any refrigeration circuit connected thereto.

The electromotive refrigerant compressor is part of a motor vehicle and includes an electric motor drive. The electromotive drive has an electric motor, which is, for example, a brushless DC motor (BLDC). Preferably, the electromotive refrigerant compressor is electrically contacted with an electrical system of the motor vehicle and / or operated with an electrical voltage of a few volts up to 1000V, in particular with an electrical voltage of 12V, 24V, 48V, 288V, 450V, 650V or 830V. By means of the electromotive refrigerant compressor, a refrigerant is compressed during operation. The refrigerant is, for example, a chemical refrigerant such as R134a or R1234yf. Alternatively, the refrigerant is C02. Preferably, the refrigerant compressor is designed such that by means of which the respective refrigerant can be compressed, for example, an increase in pressure between 5bar and 20bar. The refrigerant compressor is in particular a component of a refrigeration cycle which, for example, serves to air-conditioning an interior space or to cool an energy store of the motor vehicle, such as a high-voltage battery.

The electromotive refrigerant compressor has a power semiconductor, in particular a power semiconductor switch. The power semiconductor is provided and arranged to switch an electric current with a current of at least 1A, 2A, 5A or 10A. The power semiconductor is preferred example, a field effect transistor (FET) or IGBT. The electromotive refrigerant compressor preferably has an electronic converter, which is fed from a DC voltage network. The converter has a power output stage which in particular comprises the power semiconductor, preferably a number of such power semiconductors. The power semiconductor or semiconductors can in particular switch the currents required for the required power supply of the electric motor used. In particular, current is supplied to the electric motor by means of the power semiconductor, for which purpose preferably one terminal of the power semiconductor is electrically contacted with a winding of a stator of the electric motor. The power semiconductor is preferably a component of an output stage and / or is contacted with an electrical (DC link) capacitor. For example, the electromotive refrigerant compressor comprises a number of such power semiconductors, which are electrically interconnected in a bridge circuit, for example a B6 circuit. The electromotive refrigerant compressor further includes a temperature sensor thermally coupled to the power semiconductor. For example, the temperature sensor is mechanically directly to the power semiconductor or is coupled by means of a thermal paste or a heat pad with the power semiconductor, and / or it is measured in the eventual switching pauses the forward voltage of any freewheeling diode of the power semiconductor, which is a measure of the present on the power semiconductor first Temperature represents. Preferably, the electromotive refrigerant compressor comprises a printed circuit board with the power semiconductor, and with the temperature sensor, which simplifies manufacture and positioning.

The electromotive refrigerant compressor is operated according to a method in which a first temperature of the power semiconductor is measured, in particular by means of the temperature sensor. A second temperature of the power semiconductor is determined based on a theoretical model of the electromotive refrigerant compressor, for example, based on a theoretical model whose electric motor, in particular an operating time, an applied electrical voltage, a switched electric current and / or a number of switching operations is used. A difference between the first Temperature and the second temperature is determined and / or the gradient of the difference exceeds a fourth limit. An error is detected if the difference is greater than a first limit. Conveniently, the electromotive refrigerant compressor is suitable, and in particular provided and arranged to perform the method and in particular operated in such a way that the method is performed.

For example, the electromotive refrigerant compressor is signal technically coupled to a bus system, in particular a LIN or CAN bus. Preferably, an error is output via the BUS system. The method is provided in particular for other ancillary components of the motor vehicle.

In particular, the electromotive refrigerant compressor comprises a number of Leistungshalbeitern, which are in particular connected in parallel. In this way, an electric current carried by the respective power semiconductor is reduced, which reduces manufacturing costs. The Leistungshalbeiter are in this case thermally coupled to the same temperature sensor, wherein by means of the Leistungshalbeiter and the temperature sensor, a switching group is formed. Consequently, an average value of the temperature of the power semiconductor is measured by means of the temperature sensor. For example, between two and four power inductors are thermally coupled to the same temperature sensor. For example, the electromotive refrigerant compressor comprises a number of switching groups, each having a temperature sensor, wherein the switching groups are electrically contacted in a bridge circuit with each other. Alternatively, a complete bridge branch comprises only one of the switching groups.

An electromotive refrigerant compressor of a motor vehicle having a power semiconductor thermally coupled to a temperature sensor is used to perform a method in which a first temperature of the power semiconductor is measured, particularly by means of the temperature sensor. A second temperature of the power semiconductor is determined based on a theoretical model of the electromotive refrigerant compressor, suitably its electric motor determined, this being used in particular an operating time, an applied electrical voltage, a switched electric current and / or a number of switching operations. A difference between the first temperature and the second temperature is determined. An error is detected when the difference is greater than a first threshold and / or the gradient of the difference exceeds a fourth threshold.

The motor vehicle comprises a refrigerant circuit with an (air) condenser, as well as with an evaporator, and with an electromotive refrigerant compressor, which has a power semiconductor thermally coupled to a temperature sensor. The electromotive refrigerant compressor is operated according to a method in which a first temperature of the power semiconductor is measured, in particular by means of the temperature sensor. A second temperature of the power semiconductor is determined on the basis of a theoretical model of the electromotive refrigerant compressor, such as a theoretical model whose electric motor, in which case in particular an operating period, an applied electrical voltage, a switched electric current and / or a number of switching operations is used. A difference between the first temperature and the second temperature is determined. An error is detected if the difference is greater than a first limit.

The condenser is fluidly connected between the electromotive refrigerant compressor and the evaporator. Preferably, the refrigerant circuit comprises a further heat exchanger, which is connected between the evaporator and the electromotive refrigerant compressor, and which is preferably thermally contacted with another component of the motor vehicle, such as a blower line of an air conditioner or an energy storage, such as a high-voltage storage. The refrigerant circuit is in particular filled with a refrigerant, for example a chemical refrigerant, such as R134a, R1234yf, or with CO 2.

By means of the refrigerant compressor, a pressure of the refrigerant is increased, which is subsequently passed to the condenser, which is preferably in thermal Contact with an environment of the motor vehicle is. Preferably, by means of the capacitor, a temperature equalization of the refrigerant to the ambient temperature or at least a decrease in the temperature of the refrigerant.

With the downstream evaporator, the refrigerant is expanded, which is why the temperature of the refrigerant is further reduced. In the downstream further heat exchanger is transferred from the thermally contacted with the other heat exchanger component thermal energy to the refrigerant, resulting in a cooling of the component and heating of the refrigerant. The heated refrigerant is preferably supplied again to the refrigerant compressor for closing the refrigerant circuit.

The refinements and advantages described in connection with the method are analogously to be transferred to the electromotive refrigerant compressor or the motor vehicle and vice versa.

The invention will be explained in more detail with reference to a drawing. Show:

1 shows schematically a motor vehicle with a refrigerant compressor,

2 in a sectional view schematically simplifies the refrigerant compressor,

Fig. 3 is a plan view of a circuit board and another circuit board of

Refrigerant compressor, with a number of power semiconductors and temperature sensors, and

4 shows a method for operating the refrigerant compressor.

Corresponding parts are provided in all figures with the same reference numerals.

In Fig. 1 is a simplified simplified representation of a motor vehicle 2 with two front wheels 4 and two rear wheels 6. At least two of the wheels 4, 6 are driven by means of a main drive not shown in detail, for example a combustion engine, an electric motor or a combination thereof. The motor vehicle 2 comprises a refrigerant circuit 8, which is part of an air conditioning system. The refrigerant circuit 8 is filled with a refrigerant 10, for example, C02, R1234yf or R134a. By means of an electromotive refrigerant compressor (eKMV) 12, the refrigerant 10 is compressed and fed to a fluid-technically downstream capacitor 14, which is acted upon by ambient air, which leads to a decrease in temperature of the refrigerant 10. The pressure and thus the temperature of the refrigerant 10 is lowered by means of a downstream evaporator 16, which comprises a further heat exchanger, not shown, which is thermally coupled to a fan line of the air conditioner. The fan line promotes cooled air in an interior of the motor vehicle 2 as a function of a user setting.

The electromotive refrigerant compressor 12 is signal-coupled by means of a bus system 18, which is a CAN bus system or a Lin bus system, to a motor vehicle controller 20, such as an on-board computer. By means of a vehicle electrical system 22, which carries the respective electrical voltage, for example 48 V, and is fed by means of a battery 24, the electromotive refrigerant compressor 12 is energized. The electrical system 22 further includes a safety device 26, by means of which an electric current flow between the battery 24 and the refrigerant compressor 12 can be prevented. For this purpose, the securing device 26, for example, a load and / or circuit breaker. The safety device 26 is connected by means of the bus system 18 or otherwise signal technology with the motor vehicle control 20 so that actuated by means of the motor vehicle control 20 of the load or circuit breaker and thus the electric current flow can be prevented.

2 shows the electromotive refrigerant compressor 12 in a sectional representation along a rotation axis 28 of an electric motor 30 of the refrigerant compressor 12. The electric motor 30 has a cylindrical rotor 32 which is surrounded on the circumference by means of a hollow cylindrical stator 34. The rotor 32 comprises a number of permanent magnets and is rotatably mounted about the axis of rotation 28 by means of a shaft 36. On the shaft 36 is freiendseitig a compressor head 38 rotatably connected, for example, a scroll compressor. The stator 34 is energized by means of an electronics 40 which is connected to the bus system 18 and the vehicle electrical system 22.

The electric motor 30, the compressor head 38 and the electronics 40 are arranged in a housing 42 made of an aluminum die cast, which has a substantially hollow cylindrical shape and is concentric with the axis of rotation 28. The housing 42 comprises an inlet 44 via which the refrigerant 10 enters the housing 42 and is sucked along the electric motor 30 to the compressor head 38, by means of which an increase in pressure takes place. The compressed by means of the compressor head 38 refrigerant 10 is conveyed by means of a drain 46 from the housing 34.

The housing 42 comprises a partition wall 48, by means of which an electronics housing 50 is separated from the portion of the housing 42 through which the refrigerant 10 flows. Within the electronics housing 50, the electronics 40 is arranged. The partition wall 48 has a via 52, which is pressure-tight, and via which the energization of the stator 34 takes place. On the partition 48 in the axial direction, ie parallel to the rotation axis 28, opposite side, the electronics housing 50 comprises a housing made of a metal housing cover 54 which is releasably secured by screws to other components of the electronics housing 50, and which closes an opening of the electronics housing 50 ,

In Fig. 3, the electronics 40 is shown in a plan view. The electronics 40 has a printed circuit board 56 and a further printed circuit board 58, which, as shown in Fig. 2, in the axial direction, ie parallel to the axis of rotation 28, are arranged one above the other. The circuit board 56 is arranged parallel to the partition wall 48 and the housing cover 54, as well as the other circuit board 58. In this case, the circuit board 56 between the other circuit board 58 and the partition 48 is arranged. In Fig. 3, the two circuit boards 56, 58 shown offset in the radial direction. The further printed circuit board 58 has a bus interface 60, to which the bus system 18 is connected. With the bus interface 60 is a microprocessor 62 of further printed circuit board 58 signal coupled, which has a drive circuit 64 for power semiconductor switch 66 of the circuit board 56. For this purpose, the two printed circuit boards 58, 56 signal coupled by means of a control line 68. The power semiconductors 66 are power semiconductor switches, wherein in each case four power semiconductor switches 66, which are designed as a field-effect transistor (FET), are combined to form a switching group 70. In total, six switching groups 70 are formed here. In other words, the circuit board 56 has forty-eight power semiconductor switches 66, by means of which an electric current of up to 5A or more can be switched.

The printed circuit board 56 has a power connection 72 to which the electrical system 22 is connected. By means of the semiconductor switch 66 thus provided by means of the electrical system 22 current flow for energizing the status 34 is switched, wherein the individual switching groups 70 are contacted in a bridge circuit with each other electrically. By means of the switching groups 70, a pulse-width-modulated voltage or current signal for the stator 34 is thus provided. Here, the power semiconductors 66 of the groups of scarfs 70 are connected in parallel to each other, but at least two of the power semiconductor switches 66 of each of the switching groups 70 are connected in parallel to each other, wherein by means of the remaining two power semiconductor switch 66 in particular the remaining part of a bridge branch is formed. In other words, in this case, by means of the power semiconductors 66 of each switching group 70, a bridge branch of a bridge circuit is formed.

Each switching group 70 further includes a temperature sensor 74 thermally coupled to all the semiconductor switches 66 of the respective switching group 70. As a result, by means of the temperature sensor 74, it is possible to measure the average temperature of the switching group 70. For example, the components of each switching group 70 are thermally contacted with each other by means of a thermal paste or a heat pad. Each of the switching groups 70 further includes, for example, a capacitor not shown in more detail or is contacted with this electrically. For example, with each of the switching groups 70, an output stage is formed. FIG. 4 shows a method 76 for operating the electromotive refrigerant compressor 12, which is carried out in particular by means of the microprocessor 62. In a first step 78, a first temperature 80 is measured by means of one of the temperature sensors 74. Here, the first temperature 80 is substantially equal to the temperature of one of the power semiconductor switch 66 of the switching group 70 and the average temperature of all power semiconductor switch 66 just this switching group 70. In a second step 82, which takes place simultaneously, a second temperature 84 is just this power semiconductor switch 66th determines what a theoretical model of the electromotive refrigerant compressor 12 is used for. By means of the theoretical model 86, heating of the semiconductor switch 66 or of the switching group 70 is taken into account as a function of a previous operating time and a power and rotational speed output by means of the electric motor 30. Consequently, a theoretical heating of the semiconductor switch 66 is determined as a function of the electrical current switched by means of the respective semiconductor switch 66. The theoretical model 86 is stored in the microprocessor 62 and takes into account the drive signals generated by the drive circuit 64.

In a third operation 88, which is carried out as soon as the first temperature 80 is present, the first temperature 80 is compared with a second limit value 90, which lies between 100 ° C. and 140 ° C., for example 130 ° C. If the first temperature 80 is greater than the second limit, in a fourth step 92, the power is reduced, the electric motor 30, for which a speed of the electric motor 30 and / or the output from the electric motor 30 torque is reduced and then limited.

Once the first and second operations 78, 82 have been performed, a fifth operation 94 is performed wherein a difference 96 between the first temperature 80 and the second temperature 84 is determined, for which second temperature 84 is subtracted from the first temperature 80 , In a subsequent sixth step 98, the difference 96 with a first limit value 100, which is between 2 ° C and 20 ° C, and is for example 5 ° C. If the difference 96 is greater than the first limit value 100, ie if the second temperature 84 is greater than the first temperature 80 by the first limit value 100, a fault 104 is detected in a seventh operating step 102.

Parallel to the sixth step 98, a temperature 108 of the refrigerant 10, which is conveyed by means of the electric motor 30 and is compressed by means of the compressor head 38, is determined in an eighth step 106 on the basis of the first temperature 80 and the second temperature 84. For this purpose, for example, the difference 96 and the theoretical model 86 or a different theoretical model is used, in which the temperature determination in particular depending on the Wärmeleitkoeffizienten the partition 48 and depending on the thermal coupling of the circuit board 56 to the electronics housing 50 and / or the Partition 48 is done. To determine the temperature 108 of the refrigerant 10, it is considered that a heat transfer takes place between the power semiconductor switches 66 and the refrigerant 10. In other words, the power semiconductor switches 66 are heated or cooled by being indirectly coupled to the refrigerant 10 therethrough. In a subsequent ninth step 1 10, the temperature 108 of the refrigerant 10 is compared with a third threshold 1 12. In a subsequent thereto tenth step 1 14 an error 1 16 is detected if the temperature 108 of the refrigerant 10 is greater than the third limit value 12 1.

Furthermore, an error is detected when the first temperature 80 changes faster than the second temperature 84. For this purpose, in particular, the difference 96 is determined successively in time and a gradient of the difference 96 is determined. In summary, therefore, the error is not only detected when the (absolute) difference 96 exceeds the first limit value 100 (outside the expected limit), but also when the gradient exceeds a predetermined fourth limit value. Once an error 104, 1 16 has been detected, an eleventh step 1 18 is executed, in which the electric motor 30 is stopped. In other words, all power semiconductor switches 66 are transferred to an electrically non-conductive state. Furthermore, a twelfth operation 120 is carried out in which a warning 122 is output. The warning is transmitted by means of the bus system 18 to the on-board computer 20 and output by means of this on a display in the interior of the motor vehicle 2 and thus signals the driver of the motor vehicle 2. The method 76 is carried out in particular for each of the power semiconductor switches 66 or each of the switching groups 70, preferably on a time-parallel basis. In other words, the method 76 is executed by the microprocessor 62 six times in parallel.

The invention is not limited to the embodiment described above. Rather, other variants of the invention can be derived therefrom by the person skilled in the art without departing from the subject matter of the invention. In particular, all the individual features described in connection with the exemplary embodiment can also be combined with one another in other ways, without departing from the subject matter of the invention.

LIST OF REFERENCE NUMBERS

2 motor vehicle

4 front wheel

6 rear wheel

8 refrigerant circuit

10 refrigerants

12 electromotive refrigerant compressor

14 capacitor

16 evaporators

18 bus system

20 vehicle control

22 electrical system

24 battery

26 safety device

28 axis of rotation

30 electric motor

32 rotor

34 stator

36 wave

38 compressor head

40 electronics

42 housing

44 inlet

46 process

48 partition

50 electronics housing

52 via

54 housing cover

56 circuit board

58 more printed circuit board

60 bus interface

62 microprocessor drive circuit

Power semiconductor

drive line

switching group

power connection

temperature sensor

method

first step first temperature second step second temperature theoretical model third step second limit fourth step fifth step

difference

sixth step first limit seventh step

error

eighth step

Temperature of the refrigerant ninth step third limit tenth step

error

Eleventh work step Twelfth work step

warning

Claims

claims

1 . Method (76) for operating an electromotive refrigerant compressor (12) of a motor vehicle (2), in which

a first temperature (80) of a power semiconductor (66) is measured,

a second temperature (84) of the power semiconductor (66) is determined on the basis of a theoretical model (86) of the electromotive refrigerant compressor (12),

a difference (96) between the first temperature (80) and the second temperature (84) is determined, and

- An error (104) is detected when the difference (96) is greater than a first limit value (100).

The method (76) of claim 1, wherein the first limit (100) is greater than 2 ° C, 5 ° C or 10 ° C and less than 20 ° C.

The method (76) of claim 1 or 2, wherein a power of the electric motor (30) is reduced when the first temperature (80) is greater than a second threshold (90).

4. The method (76) as claimed in one of claims 1 to 3, wherein a temperature (108) of a refrigerant (10) conveyed by means of the electric motor (30) is determined on the basis of the first temperature (80) and the second temperature (84).

5. The method of claim 4, wherein a fault is detected when the temperature of the refrigerant is greater than a third limit.

6. The method of claim 1, wherein the electric motor is stopped and / or a warning is issued when the fault is detected.

7. An electromotive refrigerant compressor (12) of a motor vehicle (2) having a thermally with a temperature sensor (74) coupled power semiconductor (66), and which is operated according to a method (76) according to one of claims 1 to 6.

8. Electromotive refrigerant compressor (12) according to claim 7,

marked by,

a number, in particular between two and four, power inductors (66) thermally coupled to the same temperature sensor (74).

9. Use of an electromotive refrigerant compressor (12) according to claim 7 or 8 for carrying out a method (76) according to one of claims 1 to 6.

10. Motor vehicle (2) with a refrigerant circuit (8) comprising a condenser (14) and an evaporator (16) and an electromotive refrigerant compressor (12) according to claim 7 or 8.